Smoking cannabis DOES dampen your emotions ‘and increases the risk of addiction to ALL drugs’

For most people, the idea of winning some money will ignite a rush of emotions – joy, anticipation, excitement.

If you were to scan their brains at that very moment, you would see a surge of activity in the part of the brain that responds to rewards.

But, for people who’ve been smoking cannabis, that rush is not as big – and gets smaller and smaller over time, new research suggests.

And that dampened, blunted response may actually increase the risk that marijuana users are more likely to become addicted to pot and other drugs.

Dr Mary Heitzeg, senior author of the new study, a neuroscientist from the University of Michigan Medical School, said: ‘What we saw was that over time, marijuana use was associated with a lower response to a monetary reward.

‘This means that something that would be rewarding to most people was no longer rewarding to them, suggesting but not proving that their reward system has been “hijacked” by the drug, and that they need the drug to feel reward – or that their emotional response has been dampened.’

The findings come from the first long-term study of young marijuana users, that tracked brain responses to rewards over time, and is published in the JAMA Psychiatry.

They reveal measurable changes in the brain’s reward system with cannabis use – even when other factors like alcohol use and cigarette smoking were taken into account.

The study involved 108 people in their early 20s – the prime age for cannabis use.

All were taking part in a larger study of substance abuse, and all had brain scans at three points over a four-year period.

Three-quarters were men, and nearly all were white.

While MRI scans were performed, participants were invited to play a game.

People who smoke cannabis regularly show less activity in the area of the brain that releases the ‘pleasure’ hormone, dopamine

They were required to click a button when they saw a target on a screen in front of them.

Before each round, they were told they could win 20 cents, or $5 – or that they might lose that amount, have no reward or loss.

The researchers were most interested in assessing what happened to the volunteers’ brains – specifically activity in the reward center – the area called the nucleus accumbens.

And the moment that was deemed most important, was the moment of anticipation – when the volunteers knew they might win some money, and were anticipating what it would take to win the simple task.

In that moment of anticipating reward, that area of the brain should spark into action, pumping out the ‘pleasure’ hormone, dopamine.

The greater a person’s response, the more pleasure or thrill a person feels – and the more likely they will be to repeat the behavior later.

The researchers found that the more marijuana use a volunteer reported, the smaller the response in this part of the brain over time.

Past research has shown the brains of people who use a high-inducing drug repeatedly respond more prominently when they are shown cues related to that drug.

That increased response means the drug has been associated in their brains with positive, rewarding feelings.

And, that can make it harder for users to stop seeking out the drug and using it.

First author, Meghan Martz, doctoral student in developmental psychology, said: ‘It may be that the brain can drive marijuana use, and that the use of marijuana can also affect the brain.

‘We’re still unable to disentangle the cause and effect in the brain’s reward system, but studies like this can help that understanding.’

Regardless of that fact, the new findings show there is a change in the reward system over time, when a person regularly uses cannabis, the researchers noted.

Dr Heitzeg and her colleagues also showed recently in a paper in Developmental Cognitive Neuroscience that marijuana use impacts emotional functioning.

The new data on response to potentially winning money may also be further evidence that long-term marijuana use dampens a person’s emotional response – something scientists call anhedonia.

‘We are all born with an innate drive to engage in behaviors that feel rewarding and give us pleasure,’ said co-author Dr Elisa Trucco, a psychologist at the Center for Children and Families at Florida International University.

‘We now have convincing evidence that regular marijuana use impacts the brain’s natural response to these rewards.

‘In the long run, this is likely to put these individuals at risk for addiction.’

Marijuana’s reputation as a ‘safe’ drug, and one that an increasing number of states are legalizing for small-scale recreational use, means that many young people are trying it – as many as a third of college-age people report using it in the past year.

But Dr Heitzeg said that her team’s findings, and work by other addiction researchers, has shown that it can cause effects including problems with emotional functioning, academic problems, and even structural brain changes.

And, the earlier in life someone tries marijuana, the faster their transition to becoming dependent on the drug, or other substances.

‘Some people may believe that marijuana is not addictive or that it’s ‘better’ than other drugs that can cause dependence,’ said Dr Heitzeg.

‘But this study provides evidence that it’s affecting the brain in a way that may make it more difficult to stop using it.

‘It changes your brain in a way that may change your behavior, and where you get your sense of reward from.’